He served as a member of the astronaut support crew and as a capcom for the Apollo 12 lunar landing, becoming the first from the scientist-astronaut group to get a crew assignment of any kind (this happened shortly after Curt Michel resigned following several members of the class selected after theirs had gotten assigned to Apollo crews). He has also participated in the design and testing of many elements of the Skylab space station. As part of his preparation for the Skylab program, Gibson studied solar physics, ultimately writing an introductory monograph/textbook (The Quiet Sun) that is still (2006) used as a reference handbook for solar astrophysics.

Dr. Gibson was the science-pilot of Skylab 4 (third and final manned visit to the Skylab space station), launched November 16, 1973, and concluded February 8, 1974. This was the longest manned flight (84 days 1 hour 15 minutes) in history of manned space exploration at that time. Dr. Gibson was accompanied on the record-setting 34.5-million-mile flight by Gerald P. Carr (commander) and William R. Pogue (pilot). They successfully completed 56 experiments, 26 science demonstrations, 15 subsystem detailed objectives, and 13 student investigations during their 1,214 revolutions of the earth. They also acquired a wide variety of earth resources observations data using Skylab’s earth resources experiment package camera and sensor array. Dr. Gibson was the crewman primarily responsible for the 338 hours of Apollo Telescope Mount operation, which made extensive observations of solar processes.

Until March 1978, Dr. Gibson and his Skylab-4 teammates held the world record for individual time in space: 2,017 hours 15 minutes 32 seconds, and Dr. Gibson logged 15 hours and 17 minutes in three EVAs outside the orbital workshop.

Gibson resigned from NASA in December 1974 to do research on Skylab solar physics data as a senior staff scientist with the Aerospace Corporation of Los Angeles, California. Beginning in March 1976, he served for one year as a consultant to ERNO Raumfahrttechnik GmbH, in West Germany, on Spacelab design under the sponsorship of a U.S. Senior Scientist Award form the Alexander von Humboldt Foundation. In March 1977, Dr. Gibson returned to the Astronaut Office Astronaut candidate selection and training as Chief of the Scientist-Astronaut Candidates.